From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailout-de.gmx.net (mailout-de.gmx.net [213.165.64.22]) by huchra.bufferbloat.net (Postfix) with SMTP id 5E13F21F0AA for ; Wed, 23 May 2012 20:48:09 -0700 (PDT) Received: (qmail invoked by alias); 24 May 2012 03:48:07 -0000 Received: from 75-142-58-156.static.mtpk.ca.charter.com (EHLO dhcp-112.home.lan) [75.142.58.156] by mail.gmx.net (mp032) with SMTP; 24 May 2012 05:48:07 +0200 X-Authenticated: #24211782 X-Provags-ID: V01U2FsdGVkX18XEk5EApsXglbJOgfp0GqabFUnpmvjhIEGXsV1QM kbHdW0WK5+UidH Content-Type: text/plain; charset=iso-8859-1 Mime-Version: 1.0 (Apple Message framework v1278) From: Sebastian Moeller Date: Wed, 23 May 2012 20:48:04 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <1E435715-5C95-49AF-99D0-E8AD6EAD5B44@gmx.de> References: <00404BC8-3761-409D-A1C8-9213D7D9A3DF@gmx.de> To: "" X-Mailer: Apple Mail (2.1278) X-Y-GMX-Trusted: 0 Cc: codel@lists.bufferbloat.net Subject: [Codel] Fwd: [Cerowrt-devel] 3.3.6-2 X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 May 2012 03:48:10 -0000 Dear All, since Dave asked me to post out in the open here it goes: Hi Dave, hope you have had a great weekend, Maker Fair sounds sweet. And vacation = sounds even better, I hope you have/had a great time there. I managed to give 3.3.6-2 a small test drive by now on my = wndr3700v2. I have some observations I would like to report just to = document them. All my tests are using a single 5GHz wireless client = (running macosx 10.7.4) going to test sites on the internet over 30/4 = MBit cable internet. A) under moderate wireless stress I get a lot of allocation failures = from slub, like: [ 1221.664062] ath: skbuff alloc of size 1926 failed In the routers dmesg. And every now and then the router crashes and = reboots (I have not yet found a way to make this happen reliably, it = seems to require some uptime) It seems that the UDP probes used by = http://loki10.mpi-sws.mpg.de/bb/bb.php (short "bb") are quite likely to = produce those skbuff failures and also occasionally cause the crashes. = If I understand correctly this tool explicitly tries to overload the = bottleneck link with UDP packages so it can estimate the worst-case = buffering. Alas, the tool is rate limited to a few invocations per day, = so I can not really test this hypothesis in any meaningful way. = Interestingly both bb and netalyzr start reporting about 3 seconds = upstream buffering on a fresh booted router which will change to around = 38ms upstream buffering over the course of a day. And after that the = router is prone to actually reboot during a run of the 20mbit = alternative option of the bb test. Yet concurrent interactive sessions = are reactive no matter whether the reported queue is 3000 or 38 ms, so = fq_codel is pure magic. My layman's hypothesis is that somehow the UDP stream reveals a = bug in the atheros wireless driver, that occasionally takes down the = router. So this might be a different aspect of bug 379? I will try to understand netsurf better and setup a UDP stream = to see whether I can force the router to reboot reliably, as it is all I = can report is a spurious reboot. Once I have a robust reproducer I will = see whether I can make a recent openwork snapshot crash the same way. P.S.: I am currently reading up a bit on IPv6 and home security = and it seems things are more complicated than I had hoped... Best Sebastian P.P.S.: I still wrangling netperf sources to hopefully be able to = reproduce the issue (and test the UDP hypothesis) best Sebastian >=20 > On May 14, 2012, at 1:59 PM, Dave Taht wrote: >=20 >> A test release of CeroWrt is now available that has support for = Kathie >> Nichols' and Van Jacobson's new AQM, Codel , and Eric Dumazet's new >> fair queuing implementation on top of that, fq_codel. >>=20 >> fq_codel is enabled on all interfaces by default. It is vastly = simpler >> than what we were using before (sfqred) and draws upon and improves = on >> the same body of ideas (head drop, fq, timestamping) but is now tied >> to Kathie and Van's blinding insights as to a good drop strategy, and >> Eric's successor-to-sfqred ideas as towards head of queue behavior, >> modern amounts of flows, and cache line optimizations. >>=20 >> There is a simple_qos.sh script that can be set to your uplink and >> downlink speeds, but no uci interface for it as yet, nor gui. (help = on >> finishing aqm-scripts and the luci interface gladly accepted) >>=20 >> To see all the chocolately goodness of what fq_codel can do to wired >> and wireless latency, it would be good for more to play with it. >>=20 >> Benchmarks have been very good thus far, and more benchmarks and >> analysis are highly desired. >>=20 >> Caveat: >>=20 >> This release suffers from an unrelated bug ( #379 ) and should NOT be >> installed as your main router. I would love to beat this bug because >> it's the only prio 1 remaining but thus far, no luck. Under lighter >> loads CeroWrt appears to work just fine, but that's for me. YMMV. >>=20 >> Get it here: http://huchra.bufferbloat.net/~cero1/3.3/3.3.6-2/ >>=20 >>=20 >> --=20 >> Dave T=E4ht >> SKYPE: davetaht >> US Tel: 1-239-829-5608 >> http://www.bufferbloat.net >> _______________________________________________ >> Cerowrt-devel mailing list >> Cerowrt-devel@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/cerowrt-devel >=20